The present invention relates to a device or apparatus used for an electric machine comprising a casing jacket constructed with cooling ribs or fins.
Numerous different electric machine casing constructions are known. Whereas cast iron casings, particularly in low power electric machines are becoming less frequently used, sheet metal casings have enjoyed increasing favor, because such casings have advantages compared with cast casings, e.g. a lower weight, lower manufacturing expenditure, and therefore lower cost.
In the manufacture of sheet metal casings, the sheet metal is unwound from a roll of strip steel and is then pressed in a pleating or folding press to form rib elements, which are then generally shaped into circular casings and welded together at the terminal edges. Such casings are then provided with end flanges and feet or bases, followed by assembly, in the manufacture of electric machines.
However, sheet metal casings have a number of disadvantages. Thus, it is not possible, as in the case of aluminum or cast iron casings, to manufacture the feet and terminal blocks at the time of manufacturing the casing and instead an additional operation is required. The feet are mounted on the ribs and welded to the tips. However, this requires a minimum wall thickness for the ribs, so that they are suitable for the transfer of the forces which occur. The other, unstressed ribs are then overdimensioned.
The purpose of the present invention is to so construct electric machine casings of the aforementioned type, that the disadvantages of the casing formed from sheet steel ribs elements are avoided, and at the same time manufacturing costs are not increased and the heat transfer of the casing is reduced. In addition, the feet or foot parts are to be secured during the same operation as the manufacture of the ribs.